When higher efficiency, smaller size, lighter weight, and prolonged battery lifetime are required, switching regulators are used for power management as replacements for linear regulators. The most common control scheme for switching regulators is pulse-width modulation (PWM). The control uses a constant switching frequency but varies the duty cycle as the load current varies. This scheme achieves good regulation, low noise spectrum, and high efficiency at relatively heavy load. However, when the load current is low, PWM mode is inefficient due to the switching loss and the high quiescent current.
There are prior art methods to improve the efficiency of switching regulators at light load. In order to reduce switching loss, the switching frequency can be reduced, cycles can be skipped, or enter into low dropout (LDO) mode at light load. However, those solutions still may not reduce the quiescent current.